Ventilator Waveform Analysis

APPROACH

Pressure Time

  1. Determine CPAP level
  2. Is patient triggering?
  3. Shape of pressure wave

Flow Time

  1. Flow pattern
  2. Is the patient gas trapping?
  3. If patient is triggering is it pressure supported, SIMV or VAC?
  4. If patient is triggering is it pressure support or pressure controlled?
  5. Is the patient synchronizing well with ventilator?

INFORMATION TO BE GAINED

Pressure vs Time

  • type of ventilation
  • peak pressure
  • plateau pressure
  • PEEP
  • compliance calculation
  • patient triggering
  • adequacy of inspiratory flow
  • presence of auto-PEEP, presence of dynamic hyperinflation and occult PEEP
  • presence of circuit leak

Volume vs Time Graph

  • TV
  • type of flow pattern
  • inspiratory and expiratory time

Flow vs Time

  • wave form: square -> volume, decelerating -> pressure, sinusoidal
  • inspiratory time
  • expiratory time
  • auto PEEP

Pressure Volume Loops

  • compliance
  • lower inflection point
  • upper inflection point
  • PEEP level
  • peak inspiratory pressure
  • whether spontaneously breathing (effort required to trigger breath)
  • overdistension
  • leaks or airtrapping

Flow Volume Loops

  • peak inspiratory flow rate
  • peak expiratory flow rate
  • tidal volume
  • type of lung and airway pathology
  • leaks or air trapping
  • water or secretions in circuit

CCC Ventilation Series

FOAM and web resources

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the  Clinician Educator Incubator programme, and a CICM First Part Examiner.

He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.

His one great achievement is being the father of three amazing children.

On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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